title: Antimicrobial activity of nisin against the swine pathogen Streptococcus suis and its synergistic interaction with antibiotics.
abstract: Streptococcus suis serotype 2 is known to cause severe infections in pigs, including meningitis, endocarditis and pneumonia. Furthermore, this bacterium is considered an emerging zoonotic agent. Recently, increased antibiotic resistance in S. suis has been reported worldwide. The objective of this study was to evaluate the potential of nisin, a bacteriocin of the lantibiotic class, as an antibacterial agent against the pathogen S. suis serotype 2. In addition, the synergistic activity of nisin in combination with conventional antibiotics was assessed. Using a plate assay, the nisin-producing strain Lactococcus lactis ATCC 11454 proved to be capable of inhibiting the growth of S. suis (n=18) belonging to either sequence type (ST)1, ST25, or ST28. In a microdilution broth assay, the minimum inhibitory concentration (MIC) of purified nisin ranged between 1.25 and 5 μg/mL while the minimum bactericidal concentration (MBC) was between 5 and 10 μg/mL toward S. suis. The use of a capsule-deficient mutant of S. suis indicated that the presence of this polysaccharidic structure has no marked impact on susceptibility to nisin. Following treatment of S. suis with nisin, transmission electron microscopy observations revealed lysis of bacteria resulting from breakdown of the cell membrane. A time-killing curve showed a rapid bactericidal activity of nisin. Lastly, synergistic effects of nisin were observed in combination with several antibiotics, including penicillin, amoxicillin, tetracycline, streptomycin and ceftiofur. This study brought clear evidence supporting the potential of nisin for the prevention and treatment of S. suis infections in pigs.
authors.affiliation: Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, Quebec City, Quebec, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Lebel
authors.forename: Fanny
authors.initials: F
authors.lastname: Piché
authors.forename: Michel
authors.initials: M
authors.lastname: Frenette
authors.forename: Marcelo
authors.initials: M
authors.lastname: Gottschalk
authors.forename: Daniel
authors.initials: D
authors.lastname: Grenier
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016667:Bacterial Capsules / Q000187:drug effects / Q000648:ultrastructure; D015373:Bacterial Typing Techniques; D002462:Cell Membrane / Q000187:drug effects* / Q000648:ultrastructure; D002511:Cephalosporins / Q000494:pharmacology; D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D013294:Lactococcus lactis / Q000502:physiology; D008826:Microbial Sensitivity Tests; D046529:Microscopy, Electron, Transmission; D009561:Nisin / Q000494:pharmacology*; D010406:Penicillins / Q000494:pharmacology; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D017011:Streptococcus suis / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D013307:Streptomycin / Q000494:pharmacology; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy / Q000382:microbiology; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004338:Drug Combinations; D010406:Penicillins; D009561:Nisin; D000658:Amoxicillin; C053503:ceftiofur; D013752:Tetracycline; D013307:Streptomycin
keywords: Antibiotic; Nisin; Streptococcus suis; Swine infection; Synergy